1. Field of the Invention
The present invention relates to a mobile telecommunication system. Particularly, the present invention relates to a method for selecting traffic channels of a mobile telecommunication base station, in which the information capable of measuring the loads of the respective shelves is utilized, so that the selections of the traffic channel elements can be prevented from being concentrated on a particular shelf.
2. Description of the Prior Art
Generally, in a mobile telecommunication system, if a user inputs a telephone number, and presses a transmission key, the mobile station transmits an origination message to a base station. Upon receipt of the origination message, the base station allocates a traffic channel to the mobile station, and transmits the telephone number to a mobile switching center. During the time when the mobile switching center carries out the call set up, the mobile station receives base station signals through a forward channel, and begins to carry out a transmission through a reverse channel.
In this mobile communication system, if a call occurs, the conventional method for selecting the traffic channel element is such that a serial number is assigned both to the shelf and the channel card, and the channel cards are selected sequentially within the first shelf. Thus, all the available traffic channel elements are selected from the channel card, and then, a channel card is selected. In this way, when all the traffic channel elements of the channel card of the first shelf are checked, the system advances to the next shelf. Then, the traffic channel elements are selected from the next shelf based on the sequence within the channel card. When all the traffic channel elements are selected, traffic channel elements are selected from still next shelf. In this manner, conventionally, the shelves are sequentially selected, and the traffic channel elements of the channel cards are sequentially selected. Therefore, calls are concentrated on a particular shelf, while the remaining shelves and channel cards are left idle. Accordingly, even in a non-rush period, an overload is imposed, with the result that the system is grounded.
Therefore, the following method has been proposed and utilized. That is, the shelves and the traffic channel elements are assigned with index numbers. Then the shelves, the channel cards and the traffic channel elements are selected based on the index numbers, so that the selections can be uniformly dispersed to the respective shelves and channel cards.
In this method, however, the loads within the shelves are not taken into account, but the traffic channel elements are selected based only on the index numbers. In the actual operation, there are differences between the talking time periods of the subscribers. Due to these differences, if the subscribers who are assigned with the traffic channel elements of a particular shelf talk for a long time, then this particular shelf receives the greatest load. Even under this status, if more traffic channel elements are available, the selections are made, thereby more increasing the load of the shelf.